Potent and selective non-cysteine-containing inhibitors of protein farnesyltransferase

Potent and selective non-thiol-containing inhibitors of protein farnesyltransferase are described. FTI-276 (1) was transformed into pyridyl ether analogue 19. The potency of pyridyl ether 19 was improved by modification of the biphenyl core to that of an o-tolyl substituted biphenyl core to give 29. In addition to 0.4 nM in vitro potency, 29 displayed 350 nM potency in whole cells as the parent carboxylic acid. The o-tolyl biphenyl core dramatically and unexpectedly enhanced the potency of other compounds as exemplified by 46, 47, 48, and 49.

Modification of a receptor-binding surface of epidermal growth factor (EGF): analogs with enhanced receptor affinity at low pH or at neutrality

Six mutants of human epidermal growth factor (EGF), which carry single point substitutions within a surface patch proposed to juxtapose the bound receptor, were prepared and characterized for receptor affinity and mitogenicity. Receptor affinities relative to EGF are G12Q > H16D > Y13W > Q43A approximately = H16A approximately = EGF >> L15A. Notably, the reduced receptor affinity of mutant L15A indicates that Leu15 probably contributes substantially to receptor binding whereas unaltered receptor affinities observed for analogs H16A and Q43A indicate that neither His16 nor Gln43 contributes significantly to this interaction. On the other hand, the observed enhanced receptor affinities of analogs G12Q, Y13W and H16D highlight surface loci where additional productive receptor-binding contacts can be introduced. Interestingly, at acidic pH analog H16A reveals substantially greater receptor affinity than that of EGF, a property which may offer enhanced therapeutic utility in acidic environments in vivo.

Transient and heritable mutators in adaptive evolution in the lab and in nature

Major advances in understanding the molecular mechanism of recombination-dependent stationary-phase mutation in Escherichia coli occurred this past year. These advances are reviewed here, and we also present new evidence that the mutagenic state responsible is transient. We find that most stationary-phase mutants do not possess a heritable stationary-phase mutator phenotype, although a small proportion of heritable mutators was found previously. We outline similarities between this well-studied system and several recent examples of adaptive evolution associated with heritable mutator phenotype in a similarly small proportion of survivors of selection in nature and in the lab. We suggest the following: (1) Transient mutator states may also be a predominant source of adaptive mutations in these latter systems, the heritable mutators being a minority (Rosenberg 1997); (2) heritable mutators may sometimes be a product of, rather than the cause of, hypermutation that gives rise to adaptive mutations.

Dexamethasone inner ear perfusion for the treatment of Meniere's disease: a prospective, randomized, double-blind, crossover trial

OBJECTIVE

To investigate the benefits of intratympanic administration of dexamethasone in the treatment of unilateral Meniere's disease, with particular attention to the symptoms of hearing loss and tinnitus.

STUDY DESIGN

A prospective, randomized, double-blind, crossover study comparing improvements in hearing loss, tinnitus, aural fullness, and caloric vestibular response secondary to intratympanic dexamethasone and sodium hyaluronate injection versus placebo consisting of saline and sodium hyaluronate.

SETTING

A private otology/neurotology practice.

PATIENTS

Twenty patients diagnosed with either definite or probable Meniere's disease as defined by the American Academy of Otolaryngology Head and Neck Surgery Committee on Hearing and Equilibrium. All patients were < or =21 years old and were not receiving any other form of treatment for their Meniere's disease. Each patient's primary symptoms of concern were hearing loss, aural fullness, and roaring tinnitus.

INTERVENTIONS

Three consecutive daily administrations of intratympanic dexamethasone or placebo to the involved ear.

MAIN OUTCOME MEASURES

Changes in audiometric pure-tone averages, speech reception thresholds, caloric vestibular responses, scores on the tinnitus handicap inventories, questionnaires, and telephone interview responses.

RESULTS

No significant changes were observed in any measured parameter. Patients were unable to consistently identify which medication was dexamethasone and which was placebo.

CONCLUSIONS

Intratympanic administration of dexamethasone in a group of patients with unilateral Meniere's disease (Shea's stage IV) showed no benefit over placebo for the treatment of hearing loss and tinnitus.

Mismatch repair in Escherichia coli cells lacking single-strand exonucleases ExoI, ExoVII, and RecJ

In vitro, the methyl-directed mismatch repair system of Escherichia coli requires the single-strand exonuclease activity of either ExoI, ExoVII, or RecJ and possibly a fourth, unknown single-strand exonuclease. We have created the first precise null mutations in genes encoding ExoI and ExoVII and find that cells lacking these nucleases and RecJ perform mismatch repair in vivo normally such that triple-null mutants display normal mutation rates. ExoI, ExoVII, and RecJ are either redundant with another function(s) or are unnecessary for mismatch repair in vivo.

Receptor-independent role of urokinase-type plasminogen activator in pericellular plasmin and matrix metalloproteinase proteolysis during vascular wound healing in mice

It has been proposed that the urokinase receptor (u-PAR) is essential for the various biological roles of urokinase-type plasminogen activator (u-PA) in vivo, and that smooth muscle cells require u-PA for migration during arterial neointima formation. The present study was undertaken to evaluate the role of u-PAR during this process in mice with targeted disruption of the u-PAR gene (u-PAR-/-). Surprisingly, u-PAR deficiency did not affect arterial neointima formation, neointimal cell accumulation, or migration of smooth muscle cells. Indeed, topographic analysis of arterial wound healing after electric injury revealed that u-PAR-/- smooth muscle cells, originating from the uninjured borders, migrated over a similar distance and at a similar rate into the necrotic center of the wound as wild-type (u-PAR+/+) smooth muscle cells. In addition, u-PAR deficiency did not impair migration of wounded cultured smooth muscle cells in vitro. There were no genotypic differences in reendothelialization of the vascular wound. The minimal role of u-PAR in smooth muscle cell migration was not because of absent expression, since wild-type smooth muscle cells expressed u-PAR mRNA and functional receptor in vitro and in vivo. Pericellular plasmin proteolysis, evaluated by degradation of 125I-labeled fibrin and activation of zymogen matrix metalloproteinases, was similar for u-PAR-/- and u-PAR+/+ cells. Immunoelectron microscopy of injured arteries in vivo revealed that u-PA was bound on the cell surface of u-PAR+/+ cells, whereas it was present in the pericellular space around u-PAR-/- cells. Taken together, these results suggest that binding of u-PA to u-PAR is not required to provide sufficient pericellular u-PA-mediated plasmin proteolysis to allow cellular migration into a vascular wound.

Tracing the textures of an ethical relation to the dead: trauma, witnessing, and the "Montreal massacre"

This essay offers a consideration of English-language feminist memorial discourse as this has been sedimenting in Canada since the 1989 murder of 14 women at Ecole Polytechnique. The author suggests that remembrance now, almost a decade after the murders, exceeds the terms offered by a politic in which the living and the dead are connected through feminist alignment ["it could have been me"]. In its place, the author argues that there is a binding relation to the dead that is forged through understanding the murders as an event of historical trauma and rupture. She then contemplates and explores the implications of this rethinking of an ethics of relation through a situated analysis of annual memorial vigils.

Mutation for survival

Adaptive mutations appear in response to selection. In the best-studied system, the two most controversial issues were resolved this year. The mutations are neither Lamarckian nor a peculiarity of bacterial sex, as had been suggested. They occur genome-wide in a hypermutable subpopulation of stressed cells. Genomic 'hot' and 'cold' regions may explain previous failures to detect similar mutations in other systems and at other sites. Stationary phase specific limitation of mismatch repair has also been discovered.

Surgical ablation of the vestibular system in the treatment of Meniere's disease

When Meniere's disease becomes refractory to medical management, a variety of highly effective surgical options are available. A selective nerve section can relieve the disabling vertigo of Meniere's disease while preserving hearing. When the hearing on the involved side is nonserviceable, a labyrinthectomy is an important alternative. An eighth nerve section makes a complete preganglionic ablation possible with the additional benefit of relieving tinnitus in over two thirds of selected patients.

Mismatch repair protein MutL becomes limiting during stationary-phase mutation

Postsynthesis mismatch repair is an important contributor to mutation avoidance and genomic stability in bacteria, yeast, and humans. Regulation of its activity would allow organisms to regulate their ability to evolve. That mismatch repair might be down-regulated in stationary-phase Escherichia coli was suggested by the sequence spectrum of some stationary-phase ("adaptive") mutations and by the observations that MutS and MutH levels decline during stationary phase. We report that overproduction of MutL inhibits mutation in stationary phase but not during growth. MutS overproduction has no such effect, and MutL overproduction does not prevent stationary-phase decline of either MutS or MutH. These results imply that MutS and MutH decline to levels appropriate for the decreased DNA synthesis in stationary phase, whereas functional MutL is limiting for mismatch repair specifically during stationary phase. Modulation of mutation rate and genetic stability in response to environmental or developmental cues, such as stationary phase and stress, could be important in evolution, development, microbial pathogenicity, and the origins of cancer.

Laser-assisted otoendoscopy

In order to determine if laser tympanostomy is a useful adjunct to middle ear endoscopy, a retrospective case review of 95 patients over 18 years of age and requiring middle ear endoscopy was conducted in a tertiary referral center. The review revealed that clear, rapid visualization of the middle ear structures was accomplished with minimal complications. The tympanic membrane usually healed after the procedure. We conclude that laser tympanostomy safely provides a middle ear opening which streamlines the procedure by providing a bloodless field, and by greatly reducing the need for frequent cleaning of the endoscopic lens.

Genome-wide hypermutation in a subpopulation of stationary-phase cells underlies recombination-dependent adaptive mutation

Stationary-phase mutation in microbes can produce selected ('adaptive') mutants preferentially. In one system, this occurs via a distinct, recombination-dependent mechanism. Two points of controversy have surrounded these adaptive reversions of an Escherichia coli lac mutation. First, are the mutations directed preferentially to the selected gene in a Lamarckian manner? Second, is the adaptive mutation mechanism specific to the F plasmid replicon carrying lac? We report that lac adaptive mutations are associated with hypermutation in unselected genes, in all replicons in the cell. The associated mutations have a similar sequence spectrum to the adaptive reversions. Thus, the adaptive mutagenesis mechanism is not directed to the lac genes, in a Lamarckian manner, nor to the F' replicon carrying lac. Hypermutation was not found in non-revertants exposed to selection. Therefore, the genome-wide hypermutation underlying adaptive mutation occurs in a differentiated subpopulation. The existence of mutable subpopulations in non-growing cells is important in bacterial evolution and could be relevant to the somatic mutations that give rise to cancers in multicellular organisms.

A direct role for DNA polymerase III in adaptive reversion of a frameshift mutation in Escherichia coli

The sequences of adaptive reversions of a lac frameshift mutation in Escherichia coli resemble DNA polymerase errors, and the adaptive reversions decrease in strains with an antimutator DNA polymerase III (PolIII) allele. The latter finding could imply that DNA PolIII itself makes adaptive mutations. Alternatively, normal DNA PolIII errors could saturate post-synthesis mismatch repair during adaptive mutation. If so, the antimutator strain would produce fewer adaptive mutations because it possesses greater capacity for mismatch repair which could correct errors made by a polymerase other than DNA PolIII. Mismatch repair capacity is limited specifically during adaptive mutation, necessitating a test of this indirect model. This indirect model is ruled out here by the observation that the antimutator PolIII allele decreases adaptive mutation even in mismatch repair-defective cells. This supports a direct role for DNA PolIII in recombination-dependent adaptive mutation.

Requirement of receptor-bound urokinase-type plasminogen activator for integrin alphavbeta5-directed cell migration

The urokinase plasminogen activator (uPA) interacts with its cell surface receptor (uPAR), providing an inducible, localized cell surface proteolytic activity, thereby promoting cellular invasion. Evidence is provided for a novel function of cell surface-associated uPA.uPAR. Specifically, induction of cell surface expression of uPA. uPAR by growth factors or phorbol ester was necessary for vitronectin-dependent carcinoma cell migration, an event mediated by integrin alphavbeta5. Cell migration on vitronectin was blocked with either a soluble form of uPAR, an antibody that disrupts uPA binding to uPAR, or a monoclonal antibody to alphavbeta5. Moreover, plasminogen activator inhibitor type 2 blocked this migration event but did not affect adhesion, suggesting a direct role for uPA enzyme activity in this process and that migration but not adhesion of these cells is regulated by uPA.uPAR. Growth factor-mediated induction of uPA.uPAR on the carcinoma cell surface promotes a specific motility event mediated by integrin alphavbeta5, since cells transfected with the beta3 integrin subunit expressed alphavbeta3 and migrated on vitronectin independently of growth factors or uPA.uPAR expression. This relationship between alphavbeta5 and the uPA.uPAR system has significant implications for regulation of motility events associated with development, angiogenesis, and tumor metastasis.

Regulation of integrin function by the urokinase receptor

Integrin function is central to inflammation, immunity, and tumor progression. The urokinase-type plasminogen activator receptor (uPAR) and integrins formed stable complexes that both inhibited native integrin adhesive function and promoted adhesion to vitronectin via a ligand binding site on uPAR. Interaction of soluble uPAR with the active conformer of integrins mimicked the inhibitory effects of membrane uPAR. Both uPAR-mediated adhesion and altered integrin function were blocked by a peptide that bound to uPAR and disrupted complexes. These data provide a paradigm for regulation of integrins in which a nonintegrin membrane receptor interacts with and modifies the function of activated integrins.

Is plasminogen activator inhibitor-1 the molecular switch that governs urokinase receptor-mediated cell adhesion and release?

Induction of the urokinase type plasminogen activator receptor (uPAR) promotes cell adhesion through its interaction with vitronectin (VN) in the extracellular matrix, and facilitates cell migration and invasion by localizing uPA to the cell surface. We provide evidence that this balance between cell adhesion and cell detachment is governed by PA inhibitor-1 (PAI-1). First, we demonstrate that uPAR and PAI-1 bind to the same site in VN (i.e., the amino-terminal somatomedin B domain; SMB), and that PAI-1 competes with uPAR for binding to SMB. Domain swapping and mutagenesis studies indicate that the uPAR-binding sequence is located within the central region of the SMB domain, a region previously shown to contain the PAI-1-binding motif. Second, we show that PAI-1 dissociates bound VN from uPAR and detaches U937 cells from their VN substratum. This PAI-1 mediated release of cells from VN appears to occur independently of its ability to function as a protease inhibitor, and may help to explain why high PAI-1 levels indicate a poor prognosis for many cancers. Finally, we show that uPA can rapidly reverse this effect of PAI-1. Taken together, these results suggest a dynamic regulatory role for PAI-1 and uPA in uPAR-mediated cell adhesion and release.

The abused child as parent

Free-response memories and current descriptions of self, parents, babies, and significant others generated by 55 mothers who were physically abused as children were compared with memories and descriptions by 46 mothers who were not physically abused. The two groups of mothers were matched for age of baby, race, and socioeconomic status. It was found that clusters of negative attributes pervaded the memories and perceptions that abused mothers had of others, particularly parents. Moreover, the degree of negative elaboration (i.e., the number of negative clusters attributed to others) discriminated the abused and control groups almost perfectly. It was also found for both groups that the more elaborated the positive view of self and others, the more secure the attachment of infant to mother. In addition, patterns of identification and description were dramatically different between the two groups: Unlike the comparison mothers, abused mothers tended to disidentify with their own mothers and to be inconsistent in their characterization of them.

Nocturnal monitoring of growth hormone, insulin, C-peptide, and glucose in patients with acromegaly

Circulating growth hormone, insulin, C-peptide, and glucose levels were compared during the sleep state in adults with acromegaly and healthy control subjects. Growth hormone secretion was episodic in both groups, with the sleep-related growth hormone peak noticeably absent in the acromegalic subjects. The mean nocturnal plasma insulin concentration was greater in the acromegalics. There was no significant difference in the C-peptide between the two groups. Insulin and glucose levels did not show an early morning rise in either acromegalics or healthy subjects. The authors conclude that there is a marked difference in the circulating levels of growth hormone and insulin between the acromegalic and the healthy groups during the sleep state, and there is no sleep-related nocturnal growth hormone peak in the acromegalic subjects. The hyperinsulinism of patients with acromegaly cannot be attributed to excess secretion of insulin.

Urokinase receptor antagonists inhibit angiogenesis and primary tumor growth in syngeneic mice

Urokinase plasminogen activator (uPA) and its receptor are key components of a cell surface proteolytic cascade used by tumor cells and capillary endothelial cells for basement membrane invasion, a process required for metastasis and angiogenesis. We have cloned, expressed, and purified the epidermal growth factor-like domain of murine uPA alone and fused it to the Fc portion of human IgG as high-affinity murine urokinase receptor antagonists. These molecules are potent inhibitors of murine urokinase binding to its receptor and inhibit angiogenesis in an in vitro model of capillary tube formation in fibrin gels. In vivo, basic fibroblast growth factor-induced neovascularization and B16 melanoma growth in syngeneic mice are also substantially suppressed by these molecules. Coupled with previous studies showing inhibition of metastasis, these findings suggest that urokinase receptor antagonists may be useful therapeutically as inhibitors of tumor progression.